Spatially cascaded cavities for power saving distributed Raman amplification

A novel distributed amplification scheme with cascaded (using distributed in-line cavities formed by notch filters based on fiber Bragg gratings) ultra-long Raman fiber lasers for transmission with suppressed noise and reduced pump power consumption is proposed and evaluated. Comprehensive numerical analysis shows the possibility of pump power reduction by 50% compared to similar scheme without notch filters while supporting acceptable optical signal-to-noise ratio over large transmission span.